1. Field of the Invention
The present invention relates to an image processing apparatus and an image processing method for performing pattern printing, and a storage medium storing a program.
2. Description of the Related Art
In order for a user to output a desired color, color printers have color tone adjustment functions (color balance, brightness, contrast, color tone, etc.). However, there are cases where it is difficult even for an experienced person to determine what parameters to adjust and how much to adjust them. For this reason, a pattern printing function is an example of a function for a user to determine this by looking at colors output by actually printing on a printing medium. “Pattern printing” is a function for changing the color tone of a color image multiple ways, compositing them into one color image, and printing it when a determination is to be made regarding the coloration of the color image. In the flow of image data in pattern printing, image data pieces are generated by performing predetermined color adjustment on an RGB signal for input image data, and a pattern image is generated by editing the layout of those into one piece of image data. Subsequently, the image data is printed on a printing medium after undergoing color material color development processing, halftoning processing, and printer control processing.
On the other hand, a monochrome image requires pattern printing in which different color tones such as a pure black tone, a warm black tone, and a cool black tone are reproduced. However, in the case of a monochrome image, a more refined tonal expression compared to that of a color image has been requested by users, and thus a greater degree of tonal reproduction control than in the case of color images is needed. Therefore, if color image pattern printing is used as-is in a processing flow for a monochrome image, the tonality will be insufficient. Accordingly, if color processing and monochrome processing are both used, particularly in color processing using a 3DLUT, more processing control points (number of grid points in the 3DLUT) than are used in color processing are needed to satisfy requirements for a monochrome image. Also, there is another method in which color processing and monochrome processing are separated and performed in separate processing flows. Japanese Patent Laid-Open No. 2004-142423 discloses that color processing and monochrome processing are performed separately, a pattern printing image is composited based on image data that has undergone color material color development in monochrome processing, and pattern printing of a monochrome image is performed.
However, in Japanese Patent Laid-Open No. 2004-142423, color processing and monochrome processing are performed separately and a pattern printing function is added to the monochrome processing, and therefore if configured by hardware, the image processing circuit size increases, which influences the product cost. Also, since compositing of a pattern printing image is performed after color material color development, the number of image data pieces (channels) handled in compositing processing is larger in a printing apparatus using color materials such as light cyan, light magenta, and light gray in addition to CMYK. This causes an increase in the amount of memory used for compositing processing, an increase in product cost, a decrease in printing processing speed, and the like. For example, if the compositing of a pattern printing image that has undergone color material color development is performed by software, the amount of image data after color material color development rises in proportion to the number of color materials in the printing apparatus, thereby causing a decrease in printing speed.